数数

- [欧拉函数表达式推导](https://www.cnblogs.com/CQBZOIer-zyy/p/9774187.html)

- [exgcd](https://www.zybuluo.com/samzhang/note/541890)

- [同余方程](https://www.luogu.com.cn/blog/ShadderLeave/5days-equiv-from-beginner-to-killer)

- [二元一次不定方程](https://www.luogu.com.cn/blog/dengyaotriangle/solution-p5656)

- [期望](https://www.luogu.com.cn/blog/ShineEternal/mathematical-expectation)

- [矩阵乘法](https://www.luogu.com.cn/blog/shehuizhuyihao/post-zhen-sheng-fa)

- [牛顿迭代](https://www.luogu.com.cn/blog/zhang-xu-jia/niu-dun-die-dai-fa-yang-xie)

- [中国剩余定理](https://www.bilibili.com/video/BV1gf4y1S7LR)

- [反演](https://vfleaking.blog.uoj.ac/blog/87)

- [狄利克雷卷积与莫比乌斯反演](https://www.luogu.com.cn/blog/lx-2003/mobius-inversion)

- [鸽巢原理](https://www.luogu.com.cn/blog/ShineEternal/luo-gu-ri-bao)

- [线性方程组](https://www.luogu.com.cn/blog/ShineEternal/linear-equation-group)

- [容斥原理](https://www.luogu.com.cn/paste/h4hhktt3)
[容斥原理](https://www.luogu.com.cn/blog/KingSann/chu-tan-rong-chi-yuan-li)
[Min-Max容斥](https://www.luogu.com.cn/blog/command-block/min-max-rong-chi-xiao-ji)

1. P4550
2. P1654
3. UVA10288
4. P1291
5. P1850
6. P3802